Radially compressible and expandable rotor for a fluid pump

ABSTRACT

In a rotor for a fluid pump which is made radially compressible and expandable and has a hub ( 4 ) and at least one conveying element ( 10, 11, 19, 20 ) which has a plurality of struts ( 12, 13, 14, 15, 16, 21, 22, 27, 28 ) and at least one membrane ( 18 ) which can be spanned between them, provision is made for a design in accordance with the invention which is as simple and inexpensive as possible that at least one first group of struts is pivotable in a pivot plane, starting from a common base, and can thus be spanned open in the manner of a fan, wherein the conveying element lies along the hub and contacts it over its full length in the expanded state to avoid a pressure loss at the margin of the conveying element between it and the hub and thus to realize an optimum efficiency.

BACKGROUND OF THE INVENTION

The present invention is in the field of mechanical engineering andmicroengineering and in particular relates to conveying devices forliquids and fluids in general.

Such conveying devices are already known in the most variedmanifestations as pumps using different conveying principles. Rotarydrivable pumps are particularly interesting in this connection whichhave rotors which convey fluids radially or axially.

In this respect, the most varied demands are made on such pumps asregards the mounting of the rotor, the resistance toward environmentalinfluences and the interactions with the fluids to be conveyed. Inparticular on the conveying of fluids having complex, biologicallyactive molecules, e.g. inside living bodies, special demands must bemade on the relative speed between corresponding conveying elements andthe fluid as well as turbulence and shear forces.

A particular field for such pumps is in the field of microengineering inthe use in invasive medicine where pumps are manufactured in such smallconstruction that they can be moved through vessels of the body andbrought to their site of operation.

Such pumps are already known in a function as heart-assisting pumpswhich can be conducted, for example, through blood vessels in apatient's body up to and into a ventricle and can be operated there.

To optimize the efficiency of such pumps, it is also already known toequip these pumps with compressible and expandable rotors which areradially compressed during the transport through a blood vessel and canonly be expanded within a larger body space, for example in a ventricle.

The construction demands on such compressible and expandable rotors arein particular very high due to the small construction and tobiocompatibility as well as due to the demands on the reliability.

A corresponding compressible rotor is known, for example, from U.S. Pat.No. 6,860,713. Another pump of this kind is known from U.S. Pat. No.7,393,181 B2.

In this respect, it is customary for the compressibility of the rotorsto use either elastically or superelastically deformable bodies orstructures, for example of so-called memory alloys such as nitinol whichare optionally covered by a membrane so that corresponding rotors can beeasily radially elastically compressed and can be expanded or erectedautomatically or with the aid of pulling mechanisms for operation.

Rotors are also known which can be expanded in operation by thecounter-pressure of the fluid or by centrifugal forces.

The most varied mechanisms are moreover known in accordance with whichblades can be folded, bended or radially placed down in a similar mannerat corresponding hubs.

With such complex constructions, it must be ensured that the conveyingsurfaces of a corresponding conveying element are as smooth as possibleto achieve a high efficiency, that the conveying surface can beoptimized in the angle with respect to the axis of rotation and that thespeed of rotation can be selected in a meaningful range.

In addition, the compression and expansion mechanism must be given asafe design such that it works reliably, such that the pump has a stablestate in operation and such that the pump can be reliably compressed andtransported in the compressed state.

BRIEF SUMMARY OF THE INVENTION

The underlying object of the present invention against the background ofthese demands and of the prior art is to provide a pump of this kindwhich works reliably and which can be simply and reliably compressed andexpanded with a good degree of efficiency.

The object is achieved in accordance with the invention by the featuresof claim 1.

To provide a radially compressible and expandable rotor for a fluid pumphaving a hub and at least one conveying element which comprises aplurality of struts and at least one membrane which can be spannedbetween them, and to make the corresponding rotor compressible andexpandable in a particularly simple and reliable manner, the inventionprovides that at least one first group of struts is pivotable, startingfrom a common base, in a pivot plane and can thus be spanned in themanner of a fan and that, in the expanded state, the conveying elementlies along the hub and contacts it over its full length.

The surface of the conveying element is thus formed by the membranespanned between the struts and said membrane can be folded together likea fan for transport, with the struts taking up much less room radiallyin the folded state than in the spanned open state. At least some of thestruts, in particular all the struts, can be run together in the mannerof a fan at a common base and can be pivotally mounted in a simple formthere. In this case, the struts can then be spanned open for thespanning of the conveying element completely to one side of the hub at afan angle of 90° or at both sides up to the hub, for example, at anangle of 180° so that the conveying element ideally contacts the hub atboth sides of the base. A particularly good efficiency in the conveyingof fluids is realized in that pressure compensation processes of thefluid between the conveying element and the hub are minimized.

To minimize the space requirements of the conveying element or of aplurality of conveying elements if two or more conveying elements areprovided at the hub, in the compressed state, for example during thetransport of the fluid pump, provision can advantageously be made thatthe hub has a first cut-out in which at least the first group of struts,or all the struts, is/are received at least partly in the compressedstate. The hub can in this respect generally be cylindrical orcylindrically symmetrical.

In this manner, a contour of the hub is realized which radially projectsvery little, which is also smooth in dependence on the proportion ofstruts which can be accommodated within the cut-out and which makespossible a simple displacement, for example within a blood vessel.

A common pivot axis of a plurality of struts can advantageously also bearranged in the region of the first cut-out. In this case, the strutscan easily be outwardly pivoted out of the cut-out for the operation ofthe pump at the site of operation.

A particularly space-saving effect is possible when the pivot axispasses through the first cut-out and extends tangentially to theperipheral direction of the hub. In this case, the pivotable part of thestruts can be outwardly pivoted out of the cut-out, whereas a region ofthe struts at the struts in each case disposed opposite the mountingpoint is movable within the cut-out.

It can prove to be particularly advantageous if two conveying elementseach having a group of struts which can be spanned open like a fan areprovided which are disposed opposite one another at the periphery of thehub and are at least partly accommodated in a cut-out of the hub inparticular in the compressed state. In this case, two conveying elementscan be arranged symmetrically at the hub to achieve a good efficiency.Depending on the shape of the conveying elements, which can be providedas planar surfaces slanted with respect to the rotor axis, for example,or which can also have a spiral shape, provision can be made to allowdifferent conveying elements to revolve about the hub offset withrespect to one another.

In this respect, a plurality of cut-outs can be provided at theperiphery of the hub, with the presence of two conveying elements, twocut-outs, for example, which can be diametrically opposite one anotherat the periphery of the hub and which can, for example, also be combinedto a throughgoing opening of the hub. The cut-out in the hub can thus bemanufactured particularly simply from a technical production aspect andsufficient room also results for a pivot movement of the struts withinthe cut-out.

Provision can moreover advantageously be made that each of the conveyingelements lies along the hub in each case in the expanded state andcontacts it at both sides of the respective cut-out. In this case, thestruts of the conveying element at pivotable so far at both sides thatthey cover an angle of 180° along the hub and cover axially at bothsides of the cut-out, provided such a cut-out is provided, or of acorresponding pivot point, provided the conveying element is mounted atthe hub surface, and tightly contact the peripheral surface of the hub.

To achieve an ideal axial conveying and a good efficiency of the rotor,provision is advantageously provided that the membrane is inclined atleast sectionally with respect to the rotor axis in the expanded state.In this respect, depending on the angle which the membrane or theconveying surface of the conveying element adopts with respect to thelongitudinal rotor axis, a spiral rotation of the membrane about the hubcan also be provided. A planar form of the membrane can, however, alsobe provided.

An advantageous embodiment of the invention can also provide that atleast one strut is angled outward out of the pivot plane of the strutsat least over a part of its length with respect to further struts.

Any desired fluidically favorable three-dimensional shape of themembrane/conveying surface of the conveying element, which is favorablefor the conveying efficiency, can be realized by the angling or bendingof individual or groups of struts. The struts can, for example, becorrespondingly curved or angled at their ends disposed opposite thepivot axis or over the half of their length further remote from thepivot axis in order not to make a dipping into the cut-out of the hubmore difficult or to impede it in the region of the pivot axis.

A particularly simple embodiment of the rotor in accordance with theinvention provides that at least the struts of the respective groupwhich can be spanned open in the manner of a fan are pivotably mountedon a shaft within the respective cut-out. The provision of acorresponding shaft in the cut-out represents a particularly simple andpermanent solution for the pivotable mounting of the struts.

Provision, can, however, also be made that the pivotable struts areconnected to one another by film hinges at their base. For example, thestruts can be manufactured from the same material and can be madecontiguously in one piece, for example from an injection moldedmaterial. In this case, the membrane can, for example, be applied in thedipping method by dipping the struts into a liquid plastic, for examplepolyurethane; it is, however, also conceivable to manufacture themembrane from the same material as the struts with a correspondingdesign of the thickness of the membrane. In this case, the provision offilm hinges can be realized by weakening the material in the regionswhich are wanted to be correspondingly flexible.

To provide an ideal outer contour of the conveying element, it can beuseful or necessary to combine different struts with different lengthswith one another within the conveyor element. The corresponding lengthdesign of the struts can also, for example, depend on how the housing isshaped in which the rotor moves.

In addition, to increase the efficiency and to improve the stability ofthe rotor in operation, at least one reception apparatus, for example arail, for receiving the external struts of the conveying element in theexpanded state can be provided along the hub.

Accordingly, after the expansion and the fan-like spanning open of thestruts or after the spanning of the membrane, the outermost struts,which extend approximately parallel to the hub in one or both directionsaxially, starting directly from the base, can be fixed in a respectiveone of such reception apparatus which can, for example, be made infork-like form. The respective outer strut can be laid at the hub insuch a fork. A different form of fixing of the struts to the hub canalso take place, such as by magnets or by insertion into a rail-likecut-out or elevated portion of the hub.

It is thus ensured that the fluid to be conveyed cannot flow between theconveying element and the hub within the course of the pressurecompensation processes and that, on the other hand, additional purchaseand stability is given to the conveying element by the hub.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be shown and subsequently described in more detail inthe following with reference to an embodiment in a drawing. There areshown

FIG. 1 schematically, a view of a fluid pump on use as a heart catheterpump;

FIG. 2 a rotor in a view in the compressed state;

FIG. 3 an embodiment of a rotor in the expanded state;

FIG. 4 a view of a further embodiment of a rotor in the expanded state;

FIG. 5 a side view of a rotor in the compressed state;

FIG. 6 a view of the arrangement of FIG. 5 rotated by 90° about thelongitudinal rotor axis;

FIG. 7 a view as in FIGS. 5 and 6, shown three-dimensionally in anoblique view;

FIG. 8 the arrangement of FIGS. 5, 6 and 7 in an axial plan view of therotor;

FIG. 9 a side view of the rotor of FIGS. 5 to 8 in the expanded state;

FIG. 10 the view of FIG. 9 rotated by 90° about the longitudinal axis ofthe rotor;

FIG. 11 an oblique view of the arrangement of FIGS. 9 and 10;

FIG. 12 an axial plan view of the rotor of FIGS. 9 to 11;

FIG. 13 a side view of a rotor with an inclined pivot plane of thestruts;

FIG. 14 a further embodiment with a fan and a fastening to the hub; and

FIG. 15 a three-dimensional view of the conveying element as a foldedmembrane.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 schematically shows a fluid pump in which the rotor in accordancewith the invention is used after the introduction into a ventricle 1.The pump 2 has a housing 3 as well as a hub 4 to which the conveyingelements are fastened. The hub 4 is connected to a shaft 5 which isconducted through a hollow catheter 6 within a blood vessel 7 and isconducted out of it and the patient's body by a sluice 8. The rotatableshaft 5 can be driven at high revolutions, for example in the order of10,000 r.p.m., by means of a motor 9.

Blood can be conveyed between the ventricle 1 and the blood vessel, forexample sucked in by the pump 2 and pressed into the blood vessel 7, bymeans of the rotational movement transmitted onto the hub 4 and onto theconveying elements of the pump.

The pump 2 can have a diameter or general dimensions in the operatingstate which would be too large to be transported through the bloodvessel 7. The pump is radially compressible for this purpose. It isshown in FIG. 1 in the expanded state which it can adopt after theintroduction into the ventricle 1 by means of the hollow catheter 6.

The pump is pushed in the compressed state together with the hollowcatheter 6 so far through the blood vessel 7 until it projects into theventricle 1 before it is expanded.

The pump 2 has to be compressed again, which can be done, for example,by corresponding pulling elements, not shown in detail, before theremoval, which takes place by pulling out the catheter 6, or, if thepump is only expanded by centrifugal forces, it is stopped and thencollapses in on itself.

It is also conceivable to compress the pump at least a little by pullingit into the hollow catheter in that, for example, an introduction funnelis provided at the distal end of the hollow catheter 6.

The design of the hub 4 is shown in more detail in FIG. 2, with thestruts of the conveying element/elements being shown in the compressedstate, i.e. in the state placed onto the hub. The front end of the hub,which faces the inner space of the ventricle 1, is marked by 4 a.

The struts can be placed so tightly on the hub that they only take up avanishingly small space in the radial direction of the rotor. Themembrane is rolled or folded in between the struts in the compressedstate.

FIG. 3 shows the at least partly expanded state of a rotor with the hub4, with two conveying elements 10, 11 being provided which are disposeddiametrically opposite one another at the periphery of the cylindricallyformed hub 4. Each of the conveying elements generally has the shape ofa quarter of an ellipse so that the individual struts 12, 13, 14, 15, 16cover an angular range overall of approximately 90°, starting from thebase 17. However, other shapes, for example also rectangular shapes, canbe achieved by a different design of the length of the struts.

The membrane 18 is tautened flat and tight between the struts 12 to 16in the expanded state. The conveying element 10 is exactly opposite theconveying elements 11 described in more detail so that both togetherform half an ellipse in interaction with the hub 4. The struts 16contacting the hub 4 most closely can, for example, be fixed there by areception apparatus or can at least be guided. Such a receptionapparatus can, for example, be made in U shape with two limbs so thatthe strut 16 can dip into the conveying elements 11 on their expansionand is held there as required. It is thereby ensured that virtually nointermediate space arises between the strut 16 and the hub 4 which couldcause a flowing off of the fluid between the hub and the conveyingelement and thus a pressure loss if it were present on the rotation ofthe rotor.

FIG. 4 shows two semi-elliptical conveying elements 19, 20 which aredisposed opposite one another at the periphery of the hub 4 which aremade with the aid of the struts in the same way as shown in FIG. 3 andwhich axially contact the hub 4 axially at both sides of the respectivebase 17 such that a tight connection is present between the hub and theconveying element. Each of the conveying elements covers an angle of180° in accordance with FIG. 4. Other shapes, for example, rectangularshapes, can also be achieved here by a different design of the length ofthe struts. The conveying elements of FIG. 4 can also be made in asimilar manner from two respective conveying elements in accordance withFIG. 3, with in this case the respective pivot axes not having to beidentical.

The struts of an individual conveying element 19, 20 may well be ofdifferent lengths so that the base 17 does not have to lie axially atthe center of the conveying element. As shown in FIG. 4, the strut 21is, for example, shorter than the oppositely disposed strut 22.

The individual struts can, for example, be manufactured from a plasticin injection molding technology, e.g. can also be contiguous at the base17, with a membrane being spanned between the struts, either by dippingthe struts into a liquid plastic or by one-piece manufacture of theindividual conveying elements 19, 20 in the whole from the samematerial, with the membrane then being provided as a film between thestruts.

FIG. 5 shows a side view of a hub 4 having two cut-outs 23, 24 on bothsides of the hub which are connected through the hub to form a commonopening.

Two shafts 25, 26 on which the struts are pivotably mounted are fastenedin this opening. The individual struts are substantially accommodatedwithin the cut-outs 23, 24 in the compressed state, as can be seen muchmore clearly in the view of FIG. 6 which is rotated by 90° about theaxis of rotation 40 with respect to the representation of FIG. 5.

It moreover becomes clear from FIG. 6 that some of the struts 27, 28 areangled a little, at least at their respective ends remote from the pivotaxis 25, 26, out of the common pivot plane of the struts whichcorresponds to the extent of the plane of the drawing in FIG. 5. Thisdesign of the struts has the consequence that the struts cannot becompletely accommodated in the cut-outs 23, 24, but effects athree-dimensional, optimized design of the conveying element.

A three-dimensional representation of the rotor can be seen in FIG. 7which clearly shows the ends of the struts which are angled in aprojecting manner.

FIG. 8, which shows an axial plan view of the rotor of FIGS. 5 to 7,also clearly shows the projecting ends of the struts 27, 28 and of thestruts of the further conveying element disposed opposite them.

FIG. 9 shows in the expanded state of the rotor of FIGS. 5 to 8 how theangled struts 27, 28 effect a curvature of the front edge of theconveying element out of the plane of the membrane, whereby a structureof the conveying element results which is spiral in approach.

This can be seen particularly clearly from FIGS. 10 and 11 respectively.FIG. 12 also clearly shows in plan view that the membrane spannedbetween the struts is not present in a planar form, but is rathercurved.

FIG. 13 makes it clear with reference to another embodiment that thestruts 29, 30 can also be slanted with respect to their pivot plane asregards the longitudinal axis/axis of rotation 40 of the hub 4. This ispossible, for example, by a corresponding oblique position of the shaft31 on which the struts 29, 30 are pivotably mounted, as shown in FIG.13.

A spiral revolution of the conveying element/of the membrane about thehub 4 thus also results on the presence of a planar membrane between thestruts 29, 30 so that an axial propulsion of the fluid to be conveyedarises on the rotation of the hub.

The respective other pivot axis which belongs to the oppositely disposedconveying element is then likewise slanted in mirror symmetry to thepivot axis 31.

FIG. 14 shows a design of a conveying element 32 in the form of a foldedmembrane, with the individual kinks of the membrane which form thestruts being marked by 33, 34. In the present example, the kinks aremade in parallel. However, they can also be made at an angle to oneanother or curved.

The membrane can be clamped in a cut-out 35 of the hub 4 in the mannerof a fan and can be folded in axially at both sides of the hub, with themembrane stretching. A particularly simple manner of manufacture for theconveying element thus results.

The arrows 36, 37 mark the folding movements of the conveying element tothe hub 4 at both sides of the cut-out 35.

FIG. 15 shows the conveying element 38 again in isolated form as akinked membrane with the kinks/struts 33, 34 before the installationinto the cut-out 35 of the hub 4. The cut-out 35 can be introduced intothe hub as a slit, for example, with the slit also being able to extendin oblique or curved form with respect to the longitudinal axis 27 toachieve a spiral revolution of the conveying element about the hub.

A particularly inexpensive and simple manner of manufacture of theconveying elements is provided by the design in accordance with theinvention of a rotor with corresponding conveying elements whichmoreover allows a simple compression and expansion of the conveyingelements. The space requirements of the rotor on the transport into theoperating position are minimized by the invention.

The invention claimed is:
 1. A radially compressible and expandablerotor for a fluid pump having a hub and at least one conveying elementwhich has a plurality of struts and at least one membrane which can bespanned between the plurality of struts, wherein at least one firstgroup of struts is pivotable into a pivot plane, wherein each of thestruts in the group has a base which overlaps with bases of other strutsin the group, and can thus be spanned open in the manner of a fan, andwherein the at least one conveying element lies along the hub andcontacts the hub over the full length of the at least one conveyingelement in an expanded state.
 2. The rotor in accordance with claim 1,wherein a first cut-out is provided in the hub in which at least thefirst group of struts is at least partly received in a compressed state.3. The rotor in accordance with claim 2, wherein a common pivot axis ofthe plurality of struts is arranged in a region of the first cut-out. 4.The rotor in accordance with claim 3, wherein the pivot axis passesthrough the first cut-out and extends tangentially to a peripheraldirection of the hub.
 5. The rotor in accordance with claim 1, whereintwo conveying elements are provided which each have a group of strutswhich can be spanned open in the manner of a fan, which are disposedopposite one another at the periphery of the hub and which are at leastpartly received in a first cut-out of the hub in a compressed state. 6.The rotor in accordance with claim 5, wherein two cut-outs at the hubare connected to one another in a throughgoing manner and form a passageopening of the hub.
 7. The rotor in accordance with claim 1, whereineach of the at least one conveying element lies along the hub at bothsides of a respective cut-out and contacts the hub in the expanded statein each case.
 8. The rotor in accordance with claim 1, wherein the atleast one membrane is inclined at least sectionally with respect to therotor axis in the expanded state.
 9. The rotor in accordance with claim8, wherein at least one strut is angled or curved out of the pivot planeof the struts at least over a part of its length with respect to furtherstruts.
 10. The rotor in accordance with claim 1, wherein at least thestruts of the at least one first group within a respective cut-out whichcan respectively be spanned open in the manner of a fan are pivotablymounted on a shaft.
 11. The rotor in accordance with claim 1, whereinthe at least one first group of struts are connected to one another byfilm hinges at their base.
 12. The rotor in accordance with claim 1,wherein different struts having different lengths are provided.
 13. Therotor in accordance with claim 1, wherein at least one receptionapparatus, in particular a rail, is provided along the hub for areception of outer struts of the at least one conveying element in theexpanded state.
 14. The rotor in accordance with claim 1, wherein thestruts pivot about an axis which is non-parallel to a longitudinal axisof the hub.
 15. The rotor in accordance with claim 1, wherein the atleast one group of struts span open such that a path through a distalend of each of the struts forms a curve relative to a longitudinal axisof the hub.